The evaluation of quality and conformance to target production specifications for microelectronic devices frequently requires measurements of the feature sizes of the critical conductive elements for the circuits. Further, failure analysis dictates critical dimension measurements to trace the cause of failure of a device. Present commercial critical dimension measurement systems are based on secondary electron imaging techniques and analysis. Thus, in a failure analysis or quality evaluation laboratory, the microelectronic circuits examined are usually fully fabricated, with passivation and insulator layers in place. Critical dimension measurement systems based on secondary electron emission will not give accurate results unless the top insulating layer is removed. Layer removal is a destructive process and also is difficult to carry out for devices that have several metallization levels. To address the destructive analysis and layer removal problems, a novel measurement technique has been developed that uses energy dispersive x-ray analysis to measure critical feature sizes under an insulating layer.